4.8.5 Ophthalmic nerve (cranial nerve V1)
The first branch of the trigeminal, the ophthalmic nerve, passes forwards through the superior orbital fissure. As it passes through the fissure it divides. It gives off the frontal nerve which runs just beneath the roof of the orbit, and divides into cutanous branches which go to the forehead.
In addition the ophthalmic nerve gives rise to the lacrimal nerve, which supplies the lacrimal gland, and the nasociliary nerve, which gives off one or more ethmoidal nerves and a cutaneous branch, the infratrochlear nerve. Through two long ciliary nerves (here's one of them), the nasociliary nerve provides sensation to the eyeball.
The branches of the frontal nerve that we saw, emerge onto the face around the orbital margin, or through openings in it. The branches of the frontal nerve are the supra-orbital, the supratrochlear, and the infratrochlear.
These supply the forehead, the upper eyelid, and the upper part of the nose. The ethmoid branches of the nasociliary nerve supply this part of the lining of the nasal cavity.